This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This protocol is part of the Severe Asthma Research Program (SARP) sponsored by the NHLBI. The goal of the program is to characterize the distinguishing features of severe asthma in order to improve management protocols. At the University of Virginia, the investigators will test the following three hypotheses: 1. Breath condensate pH, ammonia and reduced glutathione values are lower in patients with severe asthma than in patients with mild asthma and in controls. 2. Breath condensate hydrogen peroxide and oxidized glutathione concentrations are higher in patients with severe asthma than in patients with mild asthma and in controls. 3. Airway redox changes in severe asthma result in loss of cytoprotective nitrogen oxides and formation of cytotoxic nitrogen oxide.